[jen20]

In a garage or not, it's not a normal thing to do in the UK.

It's also not a _normal_ thing to do in the US, though I have heard some people do it in higher-crime cities to avoid the windows being broken.

[userbinator]

The US is huge. In hot dry rural areas it's also perfectly normal to park with the windows down to avoid the interior getting even hotter. (And theft is not really a concern.)